In the art of forming hollow plastic articles, such as bottles, there has long been utilized a machine which takes a pre-formed tubular parison, effects the heating of such parison to a blowable temperature, encloses the heated parison in a blow mold and effects the blowing of the parison to the configuration of the desired article.
When such machines are efficiently operated, they are operated continuously, and the amount of heat applied to each parison is a function of the time during which the parison moves through a heating zone. It therefore follows that if the initial temperatures of the parisons, as supplied to the heating zone, vary substantially due to either ambient or storage conditions, such parisons will not achieve the same uniform blowing temperature that is required to insure both efficient operation of the machine and the production of quality blown containers.
Any form of in-line pre-heating apparatus, wherein the parisons are successively heated prior to being transferred to the heating area of the blow molding machine would be subject to the same defects. Moreover, whenever it is required to shut down the operation of the blow molding machine, the operator is faced with two choices, either of which is undesirable. He can either permit the in line pre-heating device to continue to operate and discard the pre-heated parisons, or he can interrupt the operation of the in line pre-heater and thereby run the risk of over-heating the parisons that are exposed to the source of heat within the pre-heating device.
There is, therefore, distinct need for a parison pre-heater which, while functioning on a batch basis, requiring only an intermittent supply of cold parisons thereto, will nevertheless deliver uniformly heated parisons to the bottle blowing machine, regardless of the speed of operation of such machine or even after the machine has been shut down momentarily for temporary repairs. The prior art has not provided a parison heating arrangement having these capabilities.